Purpose

These instructions outline the correct method for writing or updating MCU software (firmware) into the outdoor unit’s main printed wiring board (PWB) using the FM-ONE ROM Writer (Hokuto Electronic programmer).
This process ensures the control board operates with the latest firmware version, correcting logic or communication issues.

1. Preparation

Required Equipment

  • FM-ONE ROM Writer (MCU writer)

  • Writing cable

  • Inner dummy (inspection jig)

  • Breaker and power supply (AC IN)

  • Connection and power cables (A & B)

  • Checker and terminal box (E BOX)
    (see page 17 of the manual for the setup layout)

2. Wiring Connections (refer to pages 16–21)

  1. Connect the ROM writer between the outdoor unit and the inner dummy assembly.

  2. Attach the writing cable to connector CN5 (WHITE) on the outdoor unit’s MAIN PWB, labeled “MAIN – FLASH.”

  3. Verify the breaker and cables A/B connections as per the wiring diagram.

  4. Ensure the AC IN circuit is off before proceeding.

3. Writing Procedure (pages 22–26)

Step 1 – Power ON

  • Energize the outdoor unit using the breaker.

Step 2 – Confirm ROM Writer Startup

  • The FM-ONE display will illuminate, showing system version and folder selection options.

Step 3 – Select Correct Firmware Folder

Using the ▲/▼ buttons on the writer, choose the folder that matches the model (example table shown on page 23):

RegionModelBoardFolder
AustraliaAOTG45LCTLK10BS-110HUE-C1RF5212C-A70
AustraliaAOTG54LCTLK10BS-110HUE-C1RF5212C-A73

Once the correct folder (e.g. 212C-A70, 212C-A71, 212C-A73, or 212C-A69) is highlighted, press OK.

Step 4 – Execute Writing

  • When prompted “YES/NO,” select YES and press WRITE.

  • Writing takes approximately one minute.

  • Do not operate any switches during writing.

Step 5 – Completion

  • After writing completes, the display shows
    “user1 sum complete. Again? N.”
    Move the cursor to N and press OK.

  • The firmware is now stored on the board.

Step 6 – Power OFF and Disconnect

  • Turn off the outdoor unit’s power.

  • Wait until the LCD display clears, then disconnect the writing cable from CN5.

Step 7 – Label Marking

  • Apply a firmware identification label to the PWB (see example on page 27).
    The label should include the program version and date code (e.g. 150AHUE-C1 IC300_A15).

4. Verification (pages 28–30)

  1. Re-energize the unit.

  2. Confirm that the red (LED1) and green (LED2) indicators illuminate on the PWB.

  3. Use the checker box to verify successful data writing:

    • Press and hold the switch until the buzzer sounds (LED_D2 green).

    • When prompted again, press to confirm (LED_D3 orange).

  4. If all LEDs behave as specified, the ROM writing was successful.

5. Final Steps

  • Remove power and all cables.

  • Close and secure the INV CASE ASSY with screws.

  • Reassemble outer panels and carton packaging as per the reassembly instructions (pages 31–35).

  • Confirm label marking and serial identification before dispatch.

Notes

  • Work under good lighting to ensure accurate connection and labeling.

  • The writing cable must be inserted in the correct orientation (refer to connector diagram on page 21).

  • Always observe ESD precautions when handling the PWB.

Summary

The ROM writer (FM-ONE) is used to program or update control board firmware for the K10BS and K10AY outdoor series.
Following the correct connection sequence and folder selection ensures reliable software transfer.
A full verification via LED and buzzer check confirms success before final assembly.